Alkali metal silicate coating and preparation method thereof

Abstract

The present invention relates to an alkali metal silicate coating formed from alkali metal silicate represented by the chemical formula M 2 O.nSiO 2 and lithium silicate represented by the chemical formula Li 2 O.mSiO 2 , wherein M is selected from sodium, potassium, or a mixture thereof, n is from 2.9 to 3.7, m is from 4.2 to 4.8, and the molar ratio of M 2 O.nSiO 2 to Li 2 O.mSiO 2 is from 2.2 to 4.8; wherein the alkali metal silicate coating has a thickness of from 630 to 1,450 mg/m 2 , preferably from 700 to 1,400 mg/m 2 , in terms of SiO 2 as measured by fluorescent X-ray spectrometry. The present invention further relates to a preparation method of the coating. The coating of the present invention has excellent heat resistance, hot water resistance and stain resistance, as well as excellent damage resistance.

1 . An alkali metal silicate coating formed from alkali metal silicate represented by the chemical formula M 2 O.nSiO 2  and lithium silicate represented by the chemical formula Li 2 O.mSiO 2 , wherein M is selected from sodium, potassium, or a mixture thereof, n is from 2.9 to 3.7, m is from 4.2 to 4.8, and the molar ratio of M 2 O.nSiO 2  to Li 2 O.mSiO 2  is from 2.2 to 4.8;
 wherein the alkali metal silicate coating has a thickness of from 630 to 1,450 mg/m 2 , preferably from 700 to 1,400 mg/m 2 , in terms of SiO 2  as measured by fluorescent X-ray spectrometry.   
     
     
         2 . The alkali metal silicate coating according to  claim 1 , wherein the molar ratio of M 2 .nSiO 2  to Li 2 O.mSiO 2 is from 2.3 to 4.5, preferably from 2.4 to 4.4. 
     
     
         3 . The alkali metal silicate coating according to  claim 1  or  2 , wherein M is sodium or potassium. 
     
     
         4 . The alkali metal silicate coating according to any one of  claims 1  to  3 , wherein n is from 3.0 to 3.7, and/or m is from 4.3 to 4.7. 
     
     
         5 . A preparation method of an alkali metal silicate coating, comprising:
 (i) providing a mixed aqueous solution comprising alkali metal silicate represented by the chemical formula M 2 O.nSiO 2  and lithium silicate represented by the chemical formula Li 2 .mSiO 2 , wherein M is selected from sodium, potassium, or a mixture thereof, n is from 2.9 to 3.7, m is from 4.2 to 4.8, and the molar ratio of M 2 O.nSiO 2  to Li 2 O.mSiO 2  is from 2.2 to 4.8; and   (ii) coating the mixed aqueous solution in step (i) onto e surface of a substrate and then baking at a temperature of from 200 to 550° C.   
     
     
         6 . The method according to  claim 5 , wherein the molar ratio of M 2 O.nSiO 2  to Li 2 O.mSiO 2  is from 2.3 to 4.5, preferably from 2.4 to 4.4. 
     
     
         7 . The method according to  claim 5  or  6 , wherein M is sodium or potassium. 
     
     
         8 . The method according to any one of  claims 5  to  7 , wherein n is from 3.0 to 3.7, and/or m is from 4.3 to 4.7. 
     
     
         9 . The method according to any one of  claims 5  to  8 , wherein the mixed aqueous solution in step (i) is prepared by mixing an aqueous solution of alkali metal silicate represented by the chemical formula M 2 O.nSiO 2  with an aqueous solution of lithium silicate represented by the chemical formula Li 2 O.mSiO 2 . 
     
     
         10 . The method according to any one of  claims 5  to  9 , wherein the baking in step (ii) is carried out at a temperature of from 200 to 500° C., preferably from 200 to 300° C. 
     
     
         11 . The method according to any one of  claims 5  to  10 , wherein the alkali metal silicate coating has a thickness of from 630 to 1,450 mg/m 2 , preferably from 700 to 1,400 mg/m 2 , in terms of SiO 2  as measured by fluorescent X-ray spectrometry. 
     
     
         12 . The method according to any one of  claims 5  to  11 , wherein the baking in step (ii) is carried out for a duration of from 15 minutes to 2 hours, preferably from 20 minutes to 1 hour. 
     
     
         13 . The method according to any one of  claims 5  to  12 , wherein the substrate is a metal, preferably iron, aluminium, an iron alloy such as stainless steel, an aluminium alloy, or copper, and more preferably an iron alloy such as stainless steel or aluminium. 
     
     
         14 . An article having the alkali metal silicate coating according to any one of  claims 1  to  4 , or an article having an alkali metal silicate coating prepared by the method according to any one of  claims 5  to  13 . 
     
     
         15 . The article according to  claim 14 , wherein the article is a metal article, preferably an article of iron, aluminium, an iron alloy such as stainless steel, an aluminium alloy, or copper, and more preferably an article of an iron alloy such as stainless steel or aluminium. 
     
     
         16 . A product manufactured from the metal article according to  claim 14  or  15 , such as a kitchen product, a home appliance product, and a vehicle-related product. 
     
     
         17 . A method of measuring the thickness of a silicate coating by fluorescent X-ray spectrometry. 
     
     
         18 . The method according to  claim 17 , wherein the thickness of the silicate coating is from 50 to 10,000 mg/m 2 , preferably from 100 to 5,000 mg/m 2 , and more preferably from 200 to 3,000 mg/m 2 , in terms of SiO 2 . 
     
     
         19 . The method according to  claim 17  or  18 , wherein the silicate coating is the coating according to any one of  claims 1  to  4  or a coating prepared by the method according to any one of  claims 5  to  13 .